Method for the purification and separation of aryl sulphonic acids



Patented July 26, 1938 METHOD FOR THE rurtrr'rca'rrommn sur- ARATION OEARYL SULPHONIC nonls William M. Lofton, Jr.', Chicora, Jennings, H. Jones and Arthur K. Pyle, Petrolia, and Alvin A. Hoirmann, Bellevue, Pa., assignors to Pennsylvania Coal Products Company, Petr'olia; Pa., a corporation of Pennsylvania UNITE No Drawing. Application September 9, 1936, Se rial No. 100.032 e 13 Claims. (01. 260159) The present invention relates to an improved method for the purification and separation of arylsulp'honic acids. I I

One of the objects of this invention is to sepa quantity of sulphuric acid, or other suitable liquid, such as chlor sulphonic acid, in order to give suflicient fluidity to the crystallizing mixture and facilitate 'thefiltering operation and arate sulphonic acids in pure form from reaction purification of the resultant product. This is mixtures. particularly applicable to sulphonic acids of high- A further object of the invention is to greatly 1y hy roscopic nature, since otherwise these increase the yield of pure sulphonic acids obphonic acids are'not readily separated in high tained from reaction mixtures. yield from water mixtures. Instead of sulphuric .i A still further object of the invention is to acid, or chlor sulphonic acid, sulphuric acid in 1 prevent the hydration of sulphoni'c acids unh ly concentrated formis p ly used, h dergoing filtration and thereby prevent losses. s um- When sulphu a id or chlor su p Still another object of the in'vention is to enlo acid is us greater yields o he sulphonie able crystallized sulphonic acids to be more easily acids are obtained. In some instances the added w separated, as by filtration, from reaction mixtures q d can be Water- This applicable when t 15 and liquids. sulphonic acid to be separated is insoluble in Another object of the invention is to prepare water at low temperatures. pure sulphonic acids for further reactions, such If the sulphonation mixture is cooled prior to as benzene meta di-sulphonic acid for fusion with adding thereto the sulphuric acid,'or other suitcaustic alkalies in the manufacture of resorcin. a liquid, it is atltidttble t0 tritlllate the y I has heretofore been the custom in preparlized material with sulphuric acid, or the other ing a sulphonation mixture for fusion with caus- Suitable liquid. This results in breaking up the tic alkalies, or mixtures thereof, to treat the Crystals d enables the Other added liquid to mixture of sulphonic acids and excess mineral better dissolve the impurities present, and the acid presentwith lime, or other alk lin separation from these impurities is, therefore,

stances. Usually alkaline substances are selected r easily effected p t nfer ly, which form insoluble sulphates and soluble sulhowever, h liquid is added in a Suitable amount a sn such cases, the sulphates r {-11- to the sulphonation mixture, and the mixture is e ed from the soluble sulphonates. Th n t, then cooled to some desired lower temperature.

l step usually consists of forming the alkali ,11; This temperature is, preferably, as low as posof the sulphonic acid, or mixtures thereof, by Y Sible, Since the 5111131101116 acids in general treating with alkali carbonate, or like substances Crease i Solubility with 10W tempera/Cures- The whereby most oi the calcium is precipitated as temperature should not be so low, however, that a more or less insoluble salt. This leaves the freezing- OCCUIS- The temperature to which the i alkali sulphonate in solution. The water is then mixtures are cooled Varies h the Various y evaporated off by usual, suitable well known sulphonic acids" to be separated. During this methods and the'alkali salt melted with caustic coolina the mixture y be a itat d by so alkali, whereby a reaction takes place involving Suitable means whereby Smaller crystals are P f V the eliminationof the sulphonic acid group, or duced- -The Production of Small ry s a ps, and its replacement with the h d visable, since it prevents the inclusion of 1111- 40 group, or groups. It is, of cour under-stood purities. -The cooled slurry is then filtered, or that it is the salt of the sulphonic acid group, centrifuged, or separated in some other suitable as used in the reaction, that is being displaced fash on- During the filtration, Separation, it

by the alkali salt of the hydroxyl rou and is highly advisable to prevent moisture from coni that the compound containing the free hydroxyl tact with the sulphonic acids or mixturesthereof.

group is obtained upon acidifying the fusion mass. In case a pressure or vacuum filter is used, the

It has also been known in the preparation 91 air coming in contact with the filtered crystals sulphonic acids, and particularly the aryl sulshould be dried. The sulphonic acids, in general, phonic acids, that in certain cases the sulphonaare highly hygroscopic and their. great affinity tion mixture containing the sulphonic acid can for moisture causes them to removemoisturefrom be cooled and diluted by means of ice in order the air with whichthey are in contact, unless to aid in the separation of the sulphonic acid. this air is dried. If this occurs during filtration,

.It has been discovered that a great saving in losses of sulphonic'acid will result due to a portion the separation of sulphonic acid may be efiected 'of' the sulphonic acids dissolving in the water if there is added to the sulphonation mixture removed from the moist air. The air coming in in any well. known manner, as by passing through concentrated sulphuric acid, or other suitable means.

In carrying out the method in a practical manner, ithas been found advisable, but not necessary, to proceed according to the following preferred examples, in which all the proportions are given in parts by weight:

Example I 2,710 parts of so-called mixed acid, i. e., a mixture consisting essentially of benzene meta disulphonic acid together with excess sulphuric acid, is allowed to cool until the benzene meta disulphonic acid is largely crystallized out. 250 parts of sulphuric acid of 86 Baum strength is then added. The mixed acid and sulphuric acidjare triturated together, and the crystals broken up.

The slurry is then vacuum filtered; After the bulk of the liquid present is removed, the crystals are washed with an additional portion of cold sulphuric acid. A suction filter is preferably used, and all the air or other gas coming in contact with the crystals is preferably dried. The

drying of the air may be accomplished by drawing it through any suitable dehydrating agent, such as anhydrous calcium-chloride, or strong sulphuric acid. A yield of 915 parts of benzene A good yield of sulphonic acid of a meta disulphonic acid of high purity'is obtained.

. Example II 200 parts of mixed acid are mixed with 100 parts of sulphuric'acid of 66 Baum strength. a

As in Example I. mixed acid, which is cooled to'a point where substantiallyall the benzene meta disulphonic acid has been crystallized, is triturated with sulphuric acid of 66 Baum strength. It is then filtered as in Example I, and thereafter washed with one or more small -portions of a mixture of benzene and alcohol containing approximately 50% benzene, and again' filtered. The wash liquor is substantially all removed by filtration whereupon the crystals of benzene meta disulphonic acid are obtained in greater purity, but in somewhat lower yields than in Example I. 3

a Example 200 parts of mixed acid previously cooled, are mixed with 50 parts of sulphuric acid containing 20% sulphur triomde. This acid is'known commercially as' 20% oleum. The mixture is tri- 'urated and then filtered. It is filtered by means of a tightly covered funnel, and all the air drawn through, the suction filter is first passed through, sulphuric acidco'ntain'ingan excessof sulphur trioxide, as for example 65% oleum, i. e., sulphuric acid containing 65% sulphur trioxide. After substantially all of the liquid isremoved, the air entering the filtering device is further dried by passing it through, for example, anhydrous calcium chloride. By proceeding in this manner,

any water of crystallization is substantially dephonic acid were obtained.

removed by the dry air passing through the sulphonic acid. The benzene meta disulphonic acid obtained is of good quality, and the yield exceeds of the theoretical.

Example V -200 parts'of mixed acid are treated with 50 parts of 65% oleum in the same manner as that followed in Example IV.

, Example VI 200 parts of mixed acid, previously cooled, are

triturated with parts of sulphuric" acid of 98% strength. The mixture is filtered by means .of a tightly covered funnel, through which dry Example VII Phenol is sulphonated by treatment'with sulphuric acid at 100-110 C. This results in the almost exclusive sulphonation in the para position, forming para phenol sulphonic acid. The sulphonation mixture is cooled down to 5 C. while being: stirred. Crystals of phenol sulphonic acid are obtained, and these are filtered under vacuum in a manner similar to that disclosed in the previous examples. The crystals are subjected to vacuum filtration, all the air passing through the crystals being dried, until substantially all the liquid is removed. Yields of more than 40% of the theoretical of almost pure sulphonic acid are obtained.

Example VIII were filtered in the same manner as that in the previous example. 275 parts of para toluene sul- Erample IX n Benzene mono-sulphonic acid was prepared in the well known manner; phonation mixture, containing approximately 405 parts of benzene mono-sulphonic acid, were .cooled to -l0 C. The separated sulphonic acid was filtered in a manner as described in the previous examples, the filtering device being cooled during the filtering operation. 100 parts of purlfied benzene sulphonic acid .were obtained. If still greater purity of sulphonic acids is desired, it may be obtained by dissolving the purified sul-- phonic acid, after filtration, in puresulphuric acid, since the sulphonic acids are soluble in hot sulphuric acid, although insoluble in cold'sul- 'phuric acid. Caremu'st be exercised, however, to After the sul-' inthe sulphuric acids, the same methods of filtration aslthose already prevent further chemical actionl phonic acids are dissolved outlined may be used.

Example I;

Naphthalene was sulphonated in such a manner that the alpha naphthalene sulphonic acidiwaa formed. The sulphonation mixture was dilutedwith an equal amount ofwater, cooled to 5 C.

and filtered. The alpha naphthalene sulphonic' acid was obtained in yields exceeding 50% of theory.

610 parts of the sul-.

Example XI Beta naphthalene sulphonic acid wasprepared in a well known manner. 100 parts of the sulpho-' nation mixture was diluted with 63 parts of water. This mixture was cooled to 5 C. and filtered in the manner previously described. The beta naphthalene sulphonic acid was obtained in yields of 80% or greater.

It is obvious that certain minor variations may be made in the procedure, and these will be obvious to those skilled in the art. The procedure as disclosed should be considered merely as illustrative and not as limiting the scope of the invention. The sulphonic acids as thus prepared are pure, and may be used for a variety of purposes wherein such substances find applications. Such applications would naturally include reactions with caustic alkalies for production of phenols in cases in which other factors do not prohibit such use. The sulphonic acids also appear to be of particular value in electro-plating processes.

It will be readily apparent, since the sulphonic acids separated according to this improved method contain only a little sulphuric acid. that a very substantial saving is made in the amount of alkaline substances necessary to effect neutralization. Since the amount of sulphuric acid present is relatively low, it is obvious that the step of neutralizing the batch with lime, or similar substances, in the same group of elements may be dispensed with altogether in preparing the sulphonic acids for treatment with alkalies, or certain alkali salts, as well as in certain other reactions. For example,thebenzene meta disulphonic acid may be separated in substantially pure form as previously. described. If it is then desired to convert it into resorcin, the acid may be added directly to the alkali which is in suitable condition to effect the desired reaction, or more specifically, the benzene metal disulphonic acid may be added to the fused alkali, in such manner as to form resorcin. It is possible also to treat the benzene metal disulphonic acid with alkaline substances in such a manner as to produce meta phenol sulphonic acid salts from which the free acid may be obtained by proper treatment with acidic substances. Another way of making the alkali salt preparatory to treating with alkali hydroxides, would be to add the benzene metal disulphonic acid, for example, to a concentrated solution of sodium carbonate, containing an excess of sodium carbonate, the amounts of the sulphonic acid and sodium carbonate being so selected that after reaction the mixture is neutral. The excess water may be evaporated off, and the salt treated with alkali hydroxides or alkali salts, or other suitable substances.

What is claimed is:

1. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising adding an additional liquid in which the sulphonic acid is insoluble and the impurities are comparatively soluble at low temperatures thereto, mixing the resultant combined impure mixture and liquid, cooling the combined impure mixture to precipitate the aryl sulphonic acid therefrom and filtering the aryl sulphonic acid from the remainder of the mixture while maintaining the cooled mixture under dehydrating conditions.

2. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising adding concentrated sulphuric acid to the impure mixture, mixing the resultant combined impure mixture and sulphuric acid, cooling the combined impure mixture to precipitate the aryl sulphonic acid therefrom and filtering the aryl sulphonic acid from the remainder of the mixture while maintaining the cooled'mixture under dehydrating conditions.

3. A process for the separation of aryl sulphonic acids from impure mxi'tures thereof comprising adding oleum thereto, thoroughly mixing the resultant combined impure mixture and oleum, cooling the combined impure mixture and oleum to precipitate the aryl sulphonic acid therefrom and filtering the aryl sulphonic acid from the remainder of the mixture.

4. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising adding oleum thereto, thoroughly'mixing the resultant combined impure mixture and oleum, cooling the combined impure mixture and oleum to precipitate the aryl sulphonic acid therefrom and filtering the aryl sulphonic acid from the remainder of the mixture while maintaining the cooled mixture under dehydrating conditions.

5. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising cooling the sulphonated mixture to solidify the same, triturating the solidified material with a liquid in which the sulphonic acid is insoluble at low temperatures and in which the impurities are comparatively soluble and cooling the triturated mixture to precipitate the sulphonic acid therefrom and filtering the sulphonic acid from the cooled mixture.

6. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising cooling the impure mixture to crystallize the same, triturating the crystallized mixture with concentrated sulphuric acid, further cooling the triturated mixture and filtering the aryl sulphonic acid from the remainder of the cooled triturated mixture.

'7. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising cooling the impure mixture to crystallize the same, triturating the crystallized mixture with concentrated sulphuric acid, further cooling the triturated mixture and filtering the aryl sulphonic acid from the remainder of the cooled triturated mixture while maintaining the cooled mixture under dehydrating conditions.

8. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising cooling the sulphonated mixture to solidify the same, triturating the solidified material with a liquid in which the sulphonic acid is insoluble at low temperatures and in which the impurities are comparatively soluble and cooling the triturated mixture to precipitate the sulphonic acid therefrom and filtering the sulphonic acid from the cooled mixture while maintaining the cooled mixture under dehydrating conditions.

9. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising adding an additional liquid in which the sulphonic acid is insoluble at low temperatures and in which the impurities are comparatively soluble thereto, cooling the combined impure mixture and liquid to precipitate aryl sulphonic acid therefrom and filtering the precipitated impure mixture under suction while drying the air or other gas supplied to the filter during the filtering operation.

10. A process for the separation and purification of aryl sulphonic acids from impure mixtures thereof comprising adding an additional liquid in which the sulphonic acid is insoluble and in which the impurities are comparatively soluble at low temperatures and the sulphonic acid is comparatively soluble at high temperatures thereto, heating the combined impuremixture and liquid to dissolve the aryl sulphonic acid therein, cooling the combined impure mixture and liquid to precipitate aryl sulphonic acid therefrom, and filtering the precipitated varyl sulphonic acid from the remainder of the mixture under suction while drying the air or other gas applied to the filter during the filtering operation.

11. A process for the separation of aryl sulphonic acids from impure mixtures thereof comprising cooling the impure mixture to precipitate impure aryl sulphonic acid therefrom, filtering the separated sulphonic acid, adding an additional liquid in which the sulphonic acid is insoluble and in which the impurities are comparatively soluble at a low temperature and the sulphonic acid is comparatively soluble at high temperatures thereto, mixing the liquid and acid 'together, heating the combined sulphonic acid and liquid to dissolve the sulphonic acid in the liquid, cooling the combined acid and liquid to precipitate the purified sulphonic acid, and filtering the purified sulphonic acid from the remainder of the liquid under suction while drying the air or other gas applied to the filter during the filtering operation.

12. A process for the separation of highly hygroscopic aryl sulphonic acids from impure mixtures thereof which comprises cooling the mixture to a temperature suflicient to solidify the same, adding oleum thereto, triturating the solidified mixture with the oleum to dissolve the impurities therein, cooling the triturated mixture to crystallize therefrom the purified sulphonic acid, and filtering the sulphonic acid crystals from the oleum solution under dehydrating conditions so as to prevent the crystals on the filtering medium from taking up water and passing through the filter in the water solu-' tion so generated. I p

13. In a process of purifying and separating hygroscopic aryl sulphonic acids from a slurry containing a mixture of precipitated sulphonic acid and a solution of impurities, the step comprising filtering the sulphonic acid from the slurry under dehydrating conditions.

WILLIAM M. LOFTON, JR. JENNINGS H. JONES. ARTHUR K. PYLE. ALVIN A. HOFFMANN 

